CMOS image sensor is rapidly developed owing to its compatibility with the CMOS process. Compared with the manufacturing process of a CCD image sensor, the manufacturing process of a CMOS image sensor is performed by forming photosensitive elements and CMOS processing circuits together on a silicon substrate, which is completely compatible with the CMOS process, thereby greatly reducing the cost while keeping the device performance, substantially improving the integration, and enabling the production of image sensors having more pixels.
The conventional CMOS image sensor is manufactured using front side illumination (FSI) method by which the photosensitive elements and the CMOS processing circuits are formed together in a same layer on a silicon substrate, wherein the interconnects are only formed on the CMOS processing circuits without covering the photosensitive elements so as to make the light pass through. However, since the light transmission of the conventional semiconductor material is rather low, it is required to remove all of the dielectric layers formed on the photosensitive elements and then fill light-transmitting material to increase the light absorption.
However, with the shrinking of pixel size, the space between the adjacent pixels also sharply decreases; therefore, when the light is incident to a pixel, the incident light will pass through the space between the adjacent pixels into a nearby pixel after several refractions and reflections, which will produce optical crosstalk between the pixels and cause worse pixel imaging sensitivity, resolution and clarity, thus making the performance of the chip become worse. Therefore, how to reduce the optical crosstalk between the adjacent pixels and increase the incidence of light, so as to improve the pixel resolution and sensitivity is a technical problem need to be resolved by those skilled in the art.